December 10, 2013
The American Society of Heating, Refrigeration and Air-Conditioning Engineers (ASHRAE) publishes recommended ranges for temperature (65 degrees to 80 degrees F, 18 degrees to 27 degrees C) and relative humidity (20% to 80%).
One of the best ways to understand the relationship between temperature and humidity is to look at a psychrometric chart. The bottom of the chart is dry bulb temperature meaning air containing no moisture. The scale on the right of the chart is the amount of moisture in pounds contained in a pound of dry air. The curves running through the chart are the relative humidity (RH) from 0% to 100%. The temperature scale along the 100% RH curve is the wet bulb temperature.